Methods and apparatus for reestablishing a data connection with a wireless communication network

ABSTRACT

Methods and apparatus for use in a wireless communication device for communications with a wireless communication network are described. In one illustrative technique, the wireless device sends a message to the wireless network which causes data connection parameters of a previous data connection to be reset. Preferably, the message is a disconnect frame. After the message is sent, the wireless device sends a request for a new data connection to the wireless network. Thereafter, the wireless device communicates data over the new data connection with use of new data connection parameters. The data connection parameters may include an encryption parameter. The actions may be performed in response to a communication failure, such as a device reset that occurs while being out-of-coverage.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a continuation of and claims priority to U.S.continuation patent application entitled “Methods And Apparatus ForReestablishing A Data Connection With A Wireless Communication Network”having application Ser. No. 11/937,215 and filing date of 8 Nov. 2007,now U.S. Pat. No. 7,529,527, which claims priority to U.S.non-provisional patent application having application Ser. No.10/602,969 and filing date of 24 Jun. 2003, now U.S. Pat. No. 7,313,371,which claims priority to U.S. provisional patent application havingapplication No. 60/397,682 and filing date of 23 Jul. 2002, eachapplication being hereby incorporated by reference herein.

BACKGROUND

1. Field of the Technology

The present disclosure relates generally to wireless communicationdevices and associated networks, and more particularly to mobilestations communicating data within wireless communication networks suchas General Packet Radio Service (GPRS) networks.

2. Description of the Related Art

A wireless communication device, such as a mobile station, establishes apacket data protocol (PDP) context with a General Packet Radio service(GPRS) wireless network through a GPRS attach. The GPRS attach makes thewireless device known to the network by sending identification androuting area information. The wireless device goes from an idle state toa ready state if the GPRS attach is successful. During a GPRS attachprocedure, encryption parameters are established between the wirelessdevice and the GPRS network. When the data connection is resetcorrectly, both the wireless device and the GPRS network reset theirrespective encryption parameters.

During an out-of-coverage condition with the network, however, thewireless device may be powered off or reset. This will cause thewireless device to reset its data connection parameters (e.g. itsencryption parameter), but the wireless network will fail to disconnectsince the wireless device is out-of-coverage. When the wireless devicere-enters network coverage and sends a GPRS attach in attempt tore-establish a PDP context, the encryption parameter of the wirelessdevice is out-of-sync with the encryption parameter of the GPRS network.Thus, no encrypted data can be transmitted between the device and thenetwork successfully, including PDP context requests.

Accordingly, there is a resulting need for methods and apparatus forreestablishing a data connection that overcomes the deficiencies of theprior art.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of present disclosure will now be described by way ofexample with reference to attached figures, wherein:

FIG. 1 is a block diagram which illustrates pertinent components of awireless communication device which communicates within a wirelesscommunication network;

FIG. 2 is a more detailed diagram of a preferred wireless communicationdevice of FIG. 1;

FIG. 3 is a particular structure of a system for communicating with thewireless communication device;

FIGS. 4 and 5 are flowcharts which describe a method of reestablishing adata connection with a wireless communication network;

FIG. 6 is a system flow diagram relating to the method described inrelation to FIGS. 4 and 5; and

FIG. 7 is an illustration of the format of a disconnect frame which maybe used to reset network parameters of the data connection.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Methods and apparatus for use in a wireless communication device forcommunications with a wireless communication network are described. Inone illustrative technique, the wireless device sends a message to thewireless network which causes data connection parameters of a previousdata connection to be reset. Preferably, the message is a disconnectframe. After the message is sent, the wireless device sends a requestfor a new data connection to the wireless network. Thereafter, thewireless device communicates data over the new data connection with useof new data connection parameters. The data connection parameters mayinclude an encryption parameter. The actions may be performed inresponse to a communication failure, such as a device reset that occurswhile being out-of-coverage. Advantageously, a data connection issubstantially seamlessly maintained for the wireless device despitenetwork connection complexities.

FIG. 1 is a block diagram of a communication system 100 which includes amobile station 102 which communicates through a wireless communicationnetwork 104. Mobile station 102 preferably includes a visual display112, a keyboard 114, and perhaps one or more auxiliary user interfaces(UI) 116, each of which are coupled to a controller 106. Controller 106is also coupled to radio frequency (RF) transceiver circuitry 108 and anantenna 110.

Typically, controller 106 is embodied as a central processing unit (CPU)which runs operating system software in a memory component (not shown).Controller 106 will normally control overall operation of mobile station102, whereas signal processing operations associated with communicationfunctions are typically performed in RF transceiver circuitry 108.Controller 106 interfaces with device display 112 to display receivedinformation, stored information, user inputs, and the like. Keyboard114, which may be a telephone type keypad or full alphanumeric keyboard,is normally provided for entering data for storage in mobile station102, information for transmission to network 104, a telephone number toplace a telephone call, commands to be executed on mobile station 102,and possibly other or different user inputs.

Mobile station 102 sends communication signals to and receivescommunication signals from network 104 over a wireless link via antenna110. RF transceiver circuitry 108 performs functions similar to those ofstation 118 and BSC 120, including for example modulation/demodulationand possibly encoding/decoding and encryption/decryption. It is alsocontemplated that RF transceiver circuitry 108 may perform certainfunctions in addition to those performed by BSC 120. It will be apparentto those skilled in art that RF transceiver circuitry 108 will beadapted to particular wireless network or networks in which mobilestation 102 is intended to operate.

Mobile station 102 includes a battery interface 134 for receiving one ormore rechargeable batteries 132. Battery 132 provides electrical powerto electrical circuitry in mobile station 102, and battery interface 132provides for a mechanical and electrical connection for battery 132.Battery interface 132 is coupled to a regulator 136 which regulatespower to the device. When mobile station 102 is fully operational, an RFtransmitter of RF transceiver circuitry 108 is typically keyed or turnedon only when it is sending to network, and is otherwise turned off toconserve resources. Similarly, an RF receiver of RF transceivercircuitry 108 is typically periodically turned off to conserve poweruntil it is needed to receive signals or information (if at all) duringdesignated time periods.

Mobile station 102 operates using a Subscriber Identity Module (SIM) 140which is connected to or inserted in mobile station 102 at a SIMinterface 142. SIM 140 is one type of a conventional “smart card” usedto identify an end user (or subscriber) of mobile station 102 and topersonalize the device, among other things. Without SIM 140, the mobilestation terminal is not fully operational for communication throughwireless network 104. By inserting SIM 140 into mobile station 102, anend user can have access to any and all of his/her subscribed services.SIM 140 generally includes a processor and memory for storinginformation. Since SIM 140 is coupled to SIM interface 142, it iscoupled to controller 106 through communication lines 144. In order toidentify the subscriber, SIM 140 contains some user parameters such asan International Mobile Subscriber Identity (IMSI). An advantage ofusing SIM 140 is that end users are not necessarily bound by any singlephysical mobile station. SIM 140 may store additional user informationfor the mobile station as well, including datebook (or calendar)information and recent call information.

Mobile station 102 may consist of a single unit, such as a datacommunication device, a cellular telephone, a multiple-functioncommunication device with data and voice communication capabilities, apersonal digital assistant (PDA) enabled for wireless communication, ora computer incorporating an internal modem. Alternatively, mobilestation 102 may be a multiple-module unit comprising a plurality ofseparate components, including but in no way limited to a computer orother device connected to a wireless modem. In particular, for example,in the mobile station block diagram of FIG. 1, RF transceiver circuitry108 and antenna 110 may be implemented as a radio modem unit that may beinserted into a port on a laptop computer. In this case, the laptopcomputer would include display 112, keyboard 114, one or more auxiliaryUIs 116, and controller 106 embodied as the computer's CPU. It is alsocontemplated that a computer or other equipment not normally capable ofwireless communication may be adapted to connect to and effectivelyassume control of RF transceiver circuitry 108 and antenna 110 of asingle-unit device such as one of those described above. Such a mobilestation 102 may have a more particular implementation as described laterin relation to mobile station 402 of FIG. 2.

Mobile station 102 communicates in and through wireless communicationnetwork 104. In the embodiment of FIG. 1, wireless network 104 isconfigured in accordance with General Packet Radio Service (GPRS) and aGlobal Systems for Mobile (GSM) technologies. Wireless network 104includes a base station controller (BSC) 120 with an associated towerstation 118, a Mobile Switching Center (MSC) 122, a Home LocationRegister (HLR) 132, a Serving General Packet Radio Service (GPRS)Support Node (SGSN) 126, and a Gateway GPRS Support Node (GGSN) 128. MSC122 is coupled to BSC 120 and to a landline network, such as a PublicSwitched Telephone Network (PSTN) 124. SGSN 126 is coupled to BSC 120and to GGSN 128, which is in turn coupled to a public or private datanetwork 130 (such as the Internet). HLR 132 is coupled to MSC 122, SGSN126, and GGSN 128.

Station 118 is a fixed transceiver station, and station 118 and BSC 120are together referred to herein as the fixed transceiver equipment. Thefixed transceiver equipment provides wireless network coverage for aparticular coverage area commonly referred to as a “cell”. The fixedtransceiver equipment transmits communication signals to and receivescommunication signals from mobile stations within its cell via station118. The fixed transceiver equipment normally performs such functions asmodulation and possibly encoding and/or encryption of signals to betransmitted to the mobile station in accordance with particular, usuallypredetermined, communication protocols and parameters, under control ofits controller. The fixed transceiver equipment similarly demodulatesand possibly decodes and decrypts, if necessary, any communicationsignals received from mobile station 102 within its cell. Communicationprotocols and parameters may vary between different networks. Forexample, one network may employ a different modulation scheme andoperate at different frequencies than other networks.

The wireless link shown in communication system 100 of FIG. 1 representsone or more different channels, typically different radio frequency (RF)channels, and associated protocols used between wireless network 104 andmobile station 102. An RF channel is a limited resource that must beconserved, typically due to limits in overall bandwidth and a limitedbattery power of mobile station 102. Those skilled in art willappreciate that a wireless network in actual practice may includehundreds of cells, each served by a station 118 (i.e. or stationsector), depending upon desired overall expanse of network coverage. Allpertinent components may be connected by multiple switches and routers(not shown), controlled by multiple network controllers.

For all mobile station's 102 registered with a network operator,permanent data (such as mobile station 102 user's profile) as well astemporary data (such as mobile station's 102 current location) arestored in HLR 132. In case of a voice call to mobile station 102, HLR132 is queried to determine the current location of mobile station 102.A Visitor Location Register (VLR) of MSC 122 is responsible for a groupof location areas and stores the data of those mobile stations that arecurrently in its area of responsibility. This includes parts of thepermanent mobile station data that have been transmitted from HLR 132 tothe VLR for faster access. However, the VLR of MSC 122 may also assignand store local data, such as temporary identifications. Optionally, theVLR of MSC 122 can be enhanced for more efficient co-ordination of GPRSand non-GPRS services and functionality (e.g. paging forcircuit-switched calls which can be performed more efficiently via SGSN126, and combined GPRS and non-GPRS location updates).

Serving GPRS Support Node (SGSN) 126 is at the same hierarchical levelas MSC 122 and keeps track of the individual locations of mobilestations. SGSN 126 also performs security functions and access control.Gateway GPRS Support Node (GGSN) 128 provides interworking with externalpacket-switched networks and is connected with SGSNs (such as SGSN 126)via an IP-based GPRS backbone network. SGSN 126 performs authenticationand cipher setting procedures based on the same algorithms, keys, andcriteria as in existing GSM. In conventional operation, cell selectionmay be performed autonomously by mobile station 102 or by the fixedtransceiver equipment instructing mobile station 102 to select aparticular cell. Mobile station 102 informs wireless network 104 when itreselects another cell or group of cells, known as a routing area.

In order to access GPRS services, mobile station 102 first makes itspresence known to wireless network 104 by performing what is known as aGPRS “attach”. This operation establishes a logical link between mobilestation 102 and SGSN 126 and makes mobile station 102 available toreceive, for example, pages via SGSN, notifications of incoming GPRSdata, or SMS messages over GPRS. In order to send and receive GPRS data,mobile station 102 assists in activating the packet data address that itwants to use. This operation makes mobile station 102 known to GGSN 128;interworking with external data networks can thereafter commence. Userdata may be transferred transparently between mobile station 102 and theexternal data networks using, for example, encapsulation and tunneling.Data packets are equipped with GPRS-specific protocol information andtransferred between mobile station 102 and GGSN 128.

Those skilled in art will appreciate that a wireless network may beconnected to other systems, possibly including other networks, notexplicitly shown in FIG. 1. A network will normally be transmitting atvery least some sort of paging and system information on an ongoingbasis, even if there is no actual packet data exchanged. Although thenetwork consists of many parts, these parts all work together to resultin certain behaviours at the wireless link.

FIG. 2 is a detailed block diagram of a preferred mobile station 202.Mobile station 202 is preferably a two-way communication device havingat least voice and advanced data communication capabilities, includingthe capability to communicate with other computer systems. Depending onthe functionality provided by mobile station 202, it may be referred toas a data messaging device, a two-way pager, a cellular telephone withdata messaging capabilities, a wireless Internet appliance, or a datacommunication device (with or without telephony capabilities). Mobilestation 202 may communicate with any one of a plurality of fixedtransceiver stations 200 within its geographic coverage area.

Mobile station 202 will normally incorporate a communication subsystem211, which includes a receiver 212, a transmitter 214, and associatedcomponents, such as one or more (preferably embedded or internal)antenna elements 216 and 218, local oscillators (LOs) 213, and aprocessing module such as a digital signal processor (DSP) 220.Communication subsystem 211 is analogous to RF transceiver circuitry 108and antenna 110 shown in FIG. 1. As will be apparent to those skilled infield of communications, particular design of communication subsystem211 depends on the communication network in which mobile station 202 isintended to operate.

Mobile station 202 may send and receive communication signals over thenetwork after required network registration or activation procedureshave been completed. Signals received by antenna 216 through the networkare input to receiver 212, which may perform such common receiverfunctions as signal amplification, frequency down conversion, filtering,channel selection, and like, and in example shown in FIG. 2,analog-to-digital (A/D) conversion. A/D conversion of a received signalallows more complex communication functions such as demodulation anddecoding to be performed in DSP 220. In a similar manner, signals to betransmitted are processed, including modulation and encoding, forexample, by DSP 220. These DSP-processed signals are input totransmitter 214 for digital-to-analog (D/A) conversion, frequency upconversion, filtering, amplification and transmission over communicationnetwork via antenna 218. DSP 220 not only processes communicationsignals, but also provides for receiver and transmitter control. Forexample, the gains applied to communication signals in receiver 212 andtransmitter 214 may be adaptively controlled through automatic gaincontrol algorithms implemented in DSP 220.

Network access is associated with a subscriber or user of mobile station202, and therefore mobile station 202 requires a Subscriber IdentityModule or “SIM” card 262 to be inserted in a SIM interface 264 in orderto operate in the network. SIM 262 includes those features described inrelation to FIG. 1. Mobile station 202 is a battery-powered device so italso includes a battery interface 254 for receiving one or morerechargeable batteries 256. Such a battery 256 provides electrical powerto most if not all electrical circuitry in mobile station 202, andbattery interface 254 provides for a mechanical and electricalconnection for it. The battery interface 254 is coupled to a regulator(not shown) which provides power V+ to all of the circuitry.

Mobile station 202 includes a microprocessor 238 (which is oneimplementation of controller 106 of FIG. 1) which controls overalloperation of mobile station 202. Communication functions, including atleast data and voice communications, are performed through communicationsubsystem 211. Microprocessor 238 also interacts with additional devicesubsystems such as a display 222, a flash memory 224, a random accessmemory (RAM) 226, auxiliary input/output (I/O) subsystems 228, a serialport 230, a keyboard 232, a speaker 234, a microphone 236, a short-rangecommunications subsystem 240, and any other device subsystems generallydesignated at 242. Some of the subsystems shown in FIG. 2 performcommunication-related functions, whereas other subsystems may provide“resident” or on-device functions. Notably, some subsystems, such askeyboard 232 and display 222, for example, may be used for bothcommunication-related functions, such as entering a text message fortransmission over a communication network, and device-resident functionssuch as a calculator or task list. Operating system software used bymicroprocessor 238 is preferably stored in a persistent store such asflash memory 224, which may alternatively be a read-only memory (ROM) orsimilar storage element (not shown). Those skilled in the art willappreciate that the operating system, specific device applications, orparts thereof, may be temporarily loaded into a volatile store such asRAM 226.

Microprocessor 238, in addition to its operating system functions,preferably enables execution of software applications on mobile station202. A predetermined set of applications which control basic deviceoperations, including at least data and voice communication applications(such as a network reestablishment scheme), will normally be installedon mobile station 202 during its manufacture. A preferred applicationthat may be loaded onto mobile station 202 may be a personal informationmanager (PIM) application having the ability to organize and manage dataitems relating to user such as, but not limited to, e-mail, calendarevents, voice mails, appointments, and task items. Naturally, one ormore memory stores are available on mobile station 202 and SIM 256 tofacilitate storage of PIM data items and other information.

The PIM application preferably has the ability to send and receive dataitems via the wireless network. In a preferred embodiment, PIM dataitems are seamlessly integrated, synchronized, and updated via thewireless network, with the mobile station user's corresponding dataitems stored and/or associated with a host computer system therebycreating a mirrored host computer on mobile station 202 with respect tosuch items. This is especially advantageous where the host computersystem is the mobile station user's office computer system. Additionalapplications may also be loaded onto mobile station 202 through network,an auxiliary I/O subsystem 228, serial port 230, short-rangecommunications subsystem 240, or any other suitable subsystem 242, andinstalled by a user in RAM 226 or preferably a non-volatile store (notshown) for execution by microprocessor 238. Such flexibility inapplication installation increases the functionality of mobile station202 and may provide enhanced on-device functions, communication-relatedfunctions, or both. For example, secure communication applications mayenable electronic commerce functions and other such financialtransactions to be performed using mobile station 202.

In a data communication mode, a received signal such as a text message,an e-mail message, or web page download will be processed bycommunication subsystem 211 and input to microprocessor 238.Microprocessor 238 will preferably further process the signal for outputto display 222 or alternatively to auxiliary I/O device 228. A user ofmobile station 202 may also compose data items, such as e-mail messages,for example, using keyboard 232 in conjunction with display 222 andpossibly auxiliary I/O device 228. Keyboard 232 is preferably a completealphanumeric keyboard and/or telephone-type keypad. These composed itemsmay be transmitted over a communication network through communicationsubsystem 211.

For voice communications, the overall operation of mobile station 202 issubstantially similar, except that the received signals would be outputto speaker 234 and signals for transmission would be generated bymicrophone 236. Alternative voice or audio I/O subsystems, such as avoice message recording subsystem, may also be implemented on mobilestation 202. Although voice or audio signal output is preferablyaccomplished primarily through speaker 234, display 222 may also be usedto provide an indication of the identity of a calling party, duration ofa voice call, or other voice call related information, as some examples.

Serial port 230 in FIG. 2 is normally implemented in a personal digitalassistant (PDA)-type communication device for which synchronization witha user's desktop computer is a desirable, albeit optional, component.Serial port 230 enables a user to set preferences through an externaldevice or software application and extends the capabilities of mobilestation 202 by providing for information or software downloads to mobilestation 202 other than through a wireless communication network. Thealternate download path may, for example, be used to load an encryptionkey onto mobile station 202 through a direct and thus reliable andtrusted connection to thereby provide secure device communication.

Short-range communications subsystem 240 of FIG. 2 is an additionaloptional component which provides for communication between mobilestation 202 and different systems or devices, which need not necessarilybe similar devices. For example, subsystem 240 may include an infrareddevice and associated circuits and components, or a Bluetooth™communication module to provide for communication with similarly-enabledsystems and devices. Bluetooth™ is a registered trademark of BluetoothSIG, Inc.

FIG. 3 shows a particular system structure for communicating with amobile station. In particular, FIG. 3 shows basic components of anIP-based wireless data network which may be utilized. A mobile station100 communicates with a wireless packet data network 145, and may alsobe capable of communicating with a wireless voice network (not shown).As shown in FIG. 3, a gateway 140 may be coupled to an internal orexternal address resolution component 335 and one or more network entrypoints 305. Data packets are transmitted from gateway 140, which issource of information to be transmitted to mobile station 100, throughnetwork 145 by setting up a wireless network tunnel 325 from gateway 140to mobile station 100. In order to create this wireless tunnel 325, aunique network address is associated with mobile station 100. In anIP-based wireless network, however, network addresses are typically notpermanently assigned to a particular mobile station 100 but instead aredynamically allocated on an as-needed basis. It is thus preferable formobile station 100 to acquire a network address and for gateway 140 todetermine this address so as to establish wireless tunnel 325.

Network entry point 305 is generally used to multiplex and demultiplexamongst many gateways, corporate servers, and bulk connections such asthe Internet, for example. There are normally very few of these networkentry points 305, since they are also intended to centralize externallyavailable wireless network services. Network entry points 305 often usesome form of an address resolution component 335 that assists in addressassignment and lookup between gateways and mobile stations. In thisexample, address resolution component 335 is shown as a dynamic hostconfiguration protocol (DHCP) as one method for providing an addressresolution mechanism.

A central internal component of wireless data network 345 is a networkrouter 315. Normally, network routers 315 are proprietary to theparticular network, but they could alternatively be constructed fromstandard commercially available hardware. The purpose of network routers315 is to centralize thousands of fixed transceiver stations 320normally implemented in a relatively large network into a centrallocation for a long-haul connection back to network entry point 305. Insome networks there may be multiple tiers of network routers 315 andcases where there are master and slave network routers 315, but in allsuch cases the functions are similar. Often network router 315 willaccess a name server 307, in this case shown as a dynamic name server(DNS) 307 as used in the Internet, to look up destinations for routingdata messages. Fixed transceiver stations 320, as described above,provide wireless links to mobile stations such as mobile station 100.

Wireless network tunnels such as a wireless tunnel 325 are opened acrosswireless network 345 in order to allocate necessary memory, routing, andaddress resources to deliver IP packets. Such tunnels 325 areestablished as part of what are referred to as Packet Data Protocol or“PDP contexts” (i.e. data sessions). To open wireless tunnel 325, mobilestation 100 must use a specific technique associated with wirelessnetwork 345. The step of opening such a wireless tunnel 325 may requiremobile station 100 to indicate the domain, or network entry point 305with which it wishes to open wireless tunnel 325. In this example, thetunnel first reaches network router 315 which uses name server 307 todetermine which network entry point 305 matches the domain provided.Multiple wireless tunnels can be opened from one mobile station 100 forredundancy, or to access different gateways and services on the network.Once the domain name is found, the tunnel is then extended to networkentry point 305 and necessary resources are allocated at each of thenodes along the way. Network entry point 305 then uses the addressresolution (or DHCP 335) component to allocate an IP address for mobilestation 100. When an IP address has been allocated to mobile station 100and communicated to gateway 140, information can then be forwarded fromgateway 140 to mobile station 100.

Wireless tunnel 325 typically has a limited life, depending on mobilestation's 100 coverage profile and activity. Wireless network 145 willtear down wireless tunnel 325 after a certain period of inactivity orout-of-coverage period, in order to recapture resources held by thiswireless tunnel 325 for other users. The main reason for this is toreclaim the IP address temporarily reserved for mobile station 100 whenwireless tunnel 325 was first opened. Once the IP address is lost andwireless tunnel 325 is torn down, gateway 140 loses all ability toinitiate IP data packets to mobile station 100, whether overTransmission Control Protocol (TCP) or over User Datagram Protocol(UDP).

FIGS. 4 and 5 are flowcharts which describe a method of re-establishinga data connection with a wireless communication network. The flowchartof FIG. 4 pertains to device operation prior to the wireless devicebeing powered off, and the flowchart of FIG. 5 pertains to deviceoperation after the wireless device is powered back on.

Beginning at a start block 402 of FIG. 4, a wireless device (e.g. amobile station) maintains a data connection with a wirelesscommunication network (step 404). During the establishment of the dataconnection, encryption parameters between the wireless device and thenetwork are established. In this particular embodiment, the dataconnection involves both an attachment and a PDP context between thewireless device and the network. In general, an “attach” means that thewireless device is registered to the network. An attach also allows formobility (i.e. the network is able to track the wireless device'smovements). Furthermore, the wireless device is authenticated andciphering is enabled. When a Packet Data Protocol (PDP) context isactivated, an IP address is assigned for the wireless device andsubscriber-related parameters are provided so that data is capable ofbeing transferred. When a data application on the wireless device isactivated, for example, a PDP context between the between the wirelessdevice and the network is created. When the application is terminated,the PDP context ends but the registration to the wireless networkremains.

Sometime after the data connection is established, the wireless deviceexperiences a particular set of events. For one, the wireless deviceidentifies an out-of coverage condition with the network (step 406). Thewireless device may be out-of-coverage when, for example, the device canno longer successfully send or receive data through the wirelessnetwork. While being out-of-coverage, the wireless device is powered off(step 408). The powering off may be due to, for example, a manualactuation of an ON/OFF switch on the wireless device, an automaticpowering off of the wireless device, or an inadvertent reset which thewireless device experiences.

Since the wireless device is informed that it is out-of-coverage, itdoes not transmit a “detach” request to the wireless network prior tobeing shut down. Alternatively, just before being powered-off thewireless device transmits a “detach” request which is not received bythe network due to the out-of-coverage condition. The wireless devicealso resets its parameters for the data connection, including itsencryption parameter. However, the network does not reset itscorresponding network parameters for the unreleased data connection.When the encryption parameter on the device is reset, it is out-of-syncwith the encryption parameter of the wireless network.

Beginning at a start block 502 of FIG. 5, the wireless device is poweredback on (step 504). The powering back on may be due to, for example, amanual actuation of an ON/OFF switch on the wireless device, anautomatic powering on of the wireless device, or an inadvertent resetwhich the wireless device experiences. Next, the wireless deviceidentifies an in-coverage condition with the wireless network (step506). Conventionally, in this situation the wireless device transmits anattach request followed by the transmission of a PDP context request. Inat least some networks, however, no data communication is thereafterpossible because the network did not reset the former data connectionand still maintains the previous encryption parameter.

In the present disclosure, the wireless device transmits a disconnectframe message to the wireless network (step 508) prior to establishmentof an attach and PDP context. This disconnect frame causes the wirelessnetwork to reset the former data connection between the wireless deviceand the network, including resetting the network parameters (e.g. thenetwork encryption parameter) associated with the former dataconnection. Next, the wireless device transmits an attach request to thewireless network (step 510). Because the encryption parameters are nowin sync, the wireless network can communicate with the wireless device.Finally, the wireless device transmits a PDP Context request and a PDPContext is thereafter established (step 512).

FIG. 6 is a system flow diagram depicting a system flow forreestablishing a data connection with a wireless network according tothe present disclosure. Prior to the method outlined in FIG. 6, thewireless device communicates with an SGSN and, in turn, with a GGSN in aGPRS network through a base station. Sometime later, the wireless devicegoes out-of-coverage and cannot adequately communicate with anysurrounding base station. While the wireless device is out-of-coverage,it loses power and its electrical circuitry is shut down. This shut downmay be for a short or long period of time. Since the wireless device isinformed that it is out-of-coverage, it does not transmit a “detach”request to the wireless network prior to being shut down. Alternatively,just before being powered-off the wireless device transmits a “detach”request which is not received by the network due to the out-of-coveragecondition.

In accordance with the present disclosure, once the wireless deviceregains power and network coverage, it preferably transmits a disconnectframe to the GPRS network which reaches the SGSN (flow 602). Inresponse, the GPRS network resets network parameters associated with thedata connection (e.g. the encryption parameter) so that the wirelessdevice and the network may communicate again. The wireless device thenpreferably transmits a GPRS Attach request to the GPRS network whichreaches the SGSN (flow 604). In response, the SGSN informs the HLR ofthe attach and the HLR acknowledges it (flow 606). The SGSN then sendsan acceptance of the attach to the wireless device (flow 608). Next, thewireless device transmits a PDP Context Request to the SGSN (flow 610).In response, the SGSN sends a request to the GGSN to create a PDPcontext (flow 612). Because the encryption parameters of the wirelessdevice and the GGSN are now synchronized, the GGSN sends a response tothe SGSN (flow 614). Subsequently, the SGSN sends an Accept message tothe wireless device (flow 616). The data connection being fullyestablished, the wire less device goes into a standby or ready mode.

FIG. 7 is a block diagram showing a GPRS disconnect frame 700 which maybe transmitted by the wireless device when it returns to coverage afterbeing reset during an out-of-coverage condition. In the presentembodiment, this particular message causes network parameters associatedwith the old data connection to be reset so that a newly establisheddata connection can be made. However, any suitable message may beutilized to achieve the same results depending on the network.

Disconnect frame 700 is defined in the specification Logical LinkControl (LLC) Specification (GSM 04.64), which is used for packettransfer between the device and the serving SGSN. LLC layer exchangesare in frames. Disconnect frame 700 preferably consists of an addressfield 702, a control field 704, and a frame check sequence (FCS) 708.Address field 702 consists of a protocol discriminator (PD) bit 710, acommand/response (CR) bit 712, and a service access point identifier(SAPI) 714. PD bit 710 indicates what protocol the frame is using. LLCframes set PD bit 710 to ‘0’. A frame with PD bit 710 set to ‘1’ isinvalid. CR bit 712 identifies a frame as being a command or a response.If the device sends a command to the network, CR bit 712 is set to ‘0’.If the network sends a command to the device, CR bit 712 is set to ‘1’.Since disconnect frame 700 is sent from the device, CR bit 712 in thisembodiment is set to ‘0’. SAPI 714 identifies the data link controlleridentifier for which a frame is intended. In a disconnect frame, SAPIbits 1-4 are set to 1, 0, 0, 0, respectively. Control field 704identifies the type of frame and typically consists of between one andthree octets. In this case, because the frame is a control function,bits 8-6 220 are all set to ‘1’. Bit 5 722 is the poll or final bit.When the frame is issued as a command, the bit is a poll bit. When theframe is issued as a response, the bit is final bit. In this embodiment,for a disconnect frame, the remaining bits 724, bits 1-4, are preferablyset to 0, 0, 1, 0, respectively. Typically, LLC frames have aninformation field, which normally contains various commands andresponses. In a disconnect frame, no information field is permitted.Frame check sequence (FCS) field 708 consists of a 24-bit cyclicredundancy check (CRC) code. CRC-25 is used to detect bit errors in theframe header and information fields. The frame check sequence isdetermined in the specification Logical Link Control (LLC) Specification(GSM 04.64).

Final Comments. What have been described are methods and apparatus foruse in reestablishing a data connection with a wireless communicationnetwork. Initially, a wireless communication device maintains the dataconnection with the wireless communication network. During anout-of-coverage condition with the network, the wireless device ispowered off. This causes the wireless device to reset its parametersassociated with the data connection, but since the wireless device isout-of-coverage the wireless network will fail to disconnect.Preferably, after being powered back on and regaining network coverage,the wireless device transmits a message to the network which causes oneor more network parameters associated with the data connection to bereset. Subsequently, the wireless device transmits one or moreadditional messages to the network for reestablishing the dataconnection. In the preferred embodiment, the data connection is a PacketData Protocol (PDP) context with a General Packet Radio Service (GPRS)attachment, the message is a disconnect frame, and the one or moreadditional messages include a General Packet Radio Service (GPRS) attachrequest. Advantageously, a data connection is substantially seamlesslymaintained for the wireless device despite network connectioncomplexities.

The above-described embodiments of the present disclosure are intendedto be examples only. Those of skill in the art may effect alterations,modifications and variations to the particular embodiments withoutdeparting from the scope of the application. The invention describedherein in the recited claims intend to cover and embrace all suitablechanges in technology.

1. A method for use in a wireless communication device forcommunications with a wireless communication network, the methodcomprising the acts of: causing a message to be sent to the wirelessnetwork for causing data connection parameters of a previous dataconnection to be reset; causing a request for a new data connection tobe sent to the wireless network after the message is sent; andcommunicating data over the new data connection with use of new dataconnection parameters.
 2. The method of claim 1, wherein the dataconnection parameters comprise an encryption parameter.
 3. The method ofclaim 1, wherein the message comprises a disconnect frame.
 4. The methodof claim 1, wherein the data connection comprises an attachment to thewireless network.
 5. The method of claim 1, further comprising:performing the recited actions in response to a communication failure.6. The method of claim 1, wherein the data connection comprises aGeneral Packet Radio Service (GPRS) connection.
 7. The method of claim1, wherein a communication failure causes the data connection parametersin the wireless device to be reset without the data connectionparameters in the wireless network to be reset.
 8. The method of claim1, which is performed in response to a communication failure with thewireless communication network, the communication failure comprising anout-of-coverage condition between the wireless device and the wirelessnetwork.
 9. The method of claim 1, which is executed in accordance withcomputer instructions stored on a computer readable medium by one ormore processors for performing the method.
 10. The method of claim 1,wherein the message comprises a disconnect frame as defined in a LogicalLink Control (LLC) specification.
 11. A wireless communication device,comprising: a radio transceiver; one or more controllers coupled to theradio transceiver; the one or more controllers being adapted to: causinga message to be sent, to the wireless network via the radio transceiver,for causing data connection parameters of a previous data connection tobe reset; causing a request for a new data connection to be sent to thewireless network via the radio transceiver after the message is sent;and communicating data over the new data connection with the wirelessnetwork, via the radio transceiver, with use of new data connectionparameters.
 12. The wireless device of claim 11, wherein the dataconnection parameters comprise an encryption parameter.
 13. The wirelessdevice of claim 11, wherein the message comprises a disconnect frame.14. The wireless device of claim 11, wherein the one or more controllersare further adapted to maintain the new data connection by maintainingan attachment to the wireless network.
 15. The wireless device of claim11, wherein the one or more controllers are further adapted to, aftercausing the request to be sent, cause a packet data protocol (PDP)context request to be sent to the wireless network.
 16. The wirelessdevice of claim 11, wherein a communication failure occurs whichcomprises a reset of the wireless device without a successfulcommunication of a detach message to the wireless network.
 17. Thewireless device of claim 11, wherein a communication failure causes thedata connection parameters in the wireless device to be reset withoutthe data connection parameters in the wireless network to be reset. 18.The wireless device of claim 11, which is performed in response to thecommunication failure which comprises an out-of-coverage conditionbetween the wireless device and the wireless network.
 19. The wirelessdevice of claim 11, wherein the data connection comprises a GeneralPacket Radio Service (GPRS) connection.
 20. The wireless device of claim11, wherein the message comprises a disconnect frame as defined in aLogical Link Control (LLC) specification.